Beloved by many, despised by others, Thomas Kinkade's quaint rustic scenes and his wholesome image belied a dark and tortured story that contrasts with his 'sugary' artworks.

Thomas Kinkade was one of the best-selling artists in history, as well as one of the most divisive. When he died in 2012, the American painter had been rocked by business problems, but at his commercial peak a decade earlier, his company was bringing in more than $100m a year. And yet his work was despised by many critics – not because it was blasphemous or obscene, but because, well, he specialised in quaint pictures of thatched-roof rural cottages nestling in leafy groves. "Thomas Kinkade's style is illustrative saccharine fantasy rather than art with which you can connect at any meaningful level," Charlotte Mullins, the author of A Little History of Art, tells the BBC. "It is schmaltzy pastiches of Disney-style woodland scenes, complete with cutesy animals and fairy tale cottages. They are… like the images you find on cheap greetings cards – sugary and forgettable." And compared to some critics, Mullins is being polite.

These critics don't just consider Kinkade's paintings to be nauseatingly sickly, they detect something disturbing and ominous about them. In her 2003 book on California, Where I Was From, Joan Didion summed up his art by saying. "It typically featured a cottage or a house of such insistent cosiness as to seem actually sinister, suggestive of a trap designed to attract Hansel and Gretel. Every window was lit, to lurid effect, as if the interior of the structure might be on fire." As harsh as that sounds, Didion may have been more perceptive than she realised. Art for Everybody, a new documentary directed by Miranda Yousef, shows that the man who called himself the "Painter of Light" did indeed have a dark side. "His branding was so effective that you didn't know there was this really complicated and I would say tortured artist behind it all," Yousef tells the BBC. "He lived a Greek tragedy of a life."

The documentary features audio tapes recorded by Kinkade when he was a long-haired, bohemian-looking art student in California in the 1970s – and even then, he was already fretting over the question of whether he could make an impact as an artist while making a decent living. After a stint in Hollywood, painting backgrounds for Ralph Bakshi's 1983 animated feature film, Fire and Ice, he concentrated on idealised, nostalgic American landscapes, and he and his wife Nanette sold reproductions of them outside a local grocer's shop. In the 1990s, he took the idealism and the nostalgia to new heights, and swapped his rugged vistas for soft-focus pastoral scenes that a Hobbit might deem a bit on the twee side. Old-fashioned lampposts and cottage windows glowed. Streams twinkled beneath slender stone footbridges. Bushes burst with pastel flowers. And cash registers rang. Kinkade didn't sell the paintings themselves, but the hazy idylls they depicted were soon being printed on collectible plates advertised in newspapers and magazines. For many Americans, they were comforting refuges from the modern world.

In Art for Everybody, Christopher Knight, the art critic of the Los Angeles Times, is contemptuous of Kinkade's imagery. "It's a cliché piled upon a fantasy piled upon a bad idea," he says. "The colour is juiced and the light coming from inside those cottages is intense and blaring." Just as importantly, as far as his critics were concerned, Kinkade's pictures had nothing to them beyond their superficial decorative qualities. "They are banal and hollow, with no intent to say anything meaningful," says Mullins. "Today we would think they had been produced by AI – designed as if by algorithm to a certain formula." But Yousef insists that Kinkade's skill can't be discounted. "There were actually other people who were painting cottages and Christmas scenes and putting them on plates and all that stuff," she notes, "and the thing is that Kinkade's were so much better. His works just blew everybody else's out of........

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